Showing 2 results for Self-Focusing
Shadi Davoudi, Somayeh Mehrabian,
Volume 16, Issue 1 (1-2022)
Abstract
In this study, the self-guiding of an ultrashort laser pulse through air is investigated. Therefore, the terms of self-focusing, plasma defocusing and the pulse energy depletion due to the ionization, are considered in the wave equation. Then the laser pulse spot size equation is obtained using the source-dependent expansion method. Our results show that the laser pulse self-guiding occurs for the first twenty Rayleigh lengths. However, the laser pulse undergoes diffraction as it propagates further along the z axis. Moreover, it is seen that the back of the laser pulse is diffracted the most owing to the fact that the plasma is formed as the laser pulse propagates through air. It is also shown that the spot size variations affect the temporal and spatial profiles of the laser intensity, the laser pulse power and the ionization process.
Ali Mohammad Khazaei, Fatemeh Afsharipour, Hamid Reza Mashayekhi, Mohammad Yeganeh,
Volume 17, Issue 2 (6-2023)
Abstract
A new class of gratings is produced by combining the radial grating (RG) with the Fresnel zone plate (FZP). Besides having an azimuthal periodicity, these gratings focus the incident beam at a specific distance. This paper investigated the diffraction from modified Fresnel zone gratings (MFZGs) theoretically and experimentally. Our approach was to solve the Fresnel-Kirchhoff integral in the cylindrical coordinate system for a plane beam on an MFZG. The experimental results of diffraction patterns of a laser beam from the amplitude type of MFZGs confirmed the theoretical predictions well. The near-field diffraction patterns agreed with the patterns obtained from theoretical calculations.
